6024e5c395
clang 20.0.0 (based on r547379) from build 12806354. Bug: http://b/379133546 Test: N/A Change-Id: I2eb8938af55d809de674be63cb30cf27e801862b Upstream-Commit: ad834e67b1105d15ef907f6255d4c96e8e733f57
132 lines
4.2 KiB
C++
132 lines
4.2 KiB
C++
//==- TLSVariableHoist.h ------ Remove Redundant TLS Loads -------*- C++ -*-==//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass identifies/eliminates Redundant TLS Loads if related option is set.
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// For example:
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// static __thread int x;
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// int g();
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// int f(int c) {
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// int *px = &x;
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// while (c--)
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// *px += g();
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// return *px;
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// }
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//
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// will generate Redundant TLS Loads by compiling it with
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// clang++ -fPIC -ftls-model=global-dynamic -O2 -S
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//
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// .LBB0_2: # %while.body
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// # =>This Inner Loop Header: Depth=1
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// callq _Z1gv@PLT
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// movl %eax, %ebp
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// leaq _ZL1x@TLSLD(%rip), %rdi
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// callq __tls_get_addr@PLT
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// addl _ZL1x@DTPOFF(%rax), %ebp
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// movl %ebp, _ZL1x@DTPOFF(%rax)
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// addl $-1, %ebx
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// jne .LBB0_2
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// jmp .LBB0_3
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// .LBB0_4: # %entry.while.end_crit_edge
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// leaq _ZL1x@TLSLD(%rip), %rdi
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// callq __tls_get_addr@PLT
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// movl _ZL1x@DTPOFF(%rax), %ebp
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//
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// The Redundant TLS Loads will hurt the performance, especially in loops.
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// So we try to eliminate/move them if required by customers, let it be:
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//
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// # %bb.0: # %entry
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// ...
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// movl %edi, %ebx
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// leaq _ZL1x@TLSLD(%rip), %rdi
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// callq __tls_get_addr@PLT
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// leaq _ZL1x@DTPOFF(%rax), %r14
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// testl %ebx, %ebx
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// je .LBB0_1
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// .LBB0_2: # %while.body
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// # =>This Inner Loop Header: Depth=1
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// callq _Z1gv@PLT
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// addl (%r14), %eax
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// movl %eax, (%r14)
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// addl $-1, %ebx
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// jne .LBB0_2
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// jmp .LBB0_3
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_SCALAR_TLSVARIABLEHOIST_H
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#define LLVM_TRANSFORMS_SCALAR_TLSVARIABLEHOIST_H
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#include "llvm/ADT/MapVector.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/IR/PassManager.h"
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namespace llvm {
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class BasicBlock;
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class DominatorTree;
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class Function;
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class GlobalVariable;
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class Instruction;
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/// A private "module" namespace for types and utilities used by
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/// TLSVariableHoist. These are implementation details and should
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/// not be used by clients.
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namespace tlshoist {
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/// Keeps track of the user of a TLS variable and the operand index
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/// where the variable is used.
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struct TLSUser {
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Instruction *Inst;
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unsigned OpndIdx;
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TLSUser(Instruction *Inst, unsigned Idx) : Inst(Inst), OpndIdx(Idx) {}
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};
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/// Keeps track of a TLS variable candidate and its users.
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struct TLSCandidate {
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SmallVector<TLSUser, 8> Users;
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/// Add the user to the use list and update the cost.
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void addUser(Instruction *Inst, unsigned Idx) {
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Users.push_back(TLSUser(Inst, Idx));
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}
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};
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} // end namespace tlshoist
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class TLSVariableHoistPass : public PassInfoMixin<TLSVariableHoistPass> {
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public:
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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// Glue for old PM.
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bool runImpl(Function &F, DominatorTree &DT, LoopInfo &LI);
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private:
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DominatorTree *DT;
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LoopInfo *LI;
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/// Keeps track of TLS variable candidates found in the function.
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using TLSCandMapType = MapVector<GlobalVariable *, tlshoist::TLSCandidate>;
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TLSCandMapType TLSCandMap;
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void collectTLSCandidates(Function &Fn);
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void collectTLSCandidate(Instruction *Inst);
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Instruction *getNearestLoopDomInst(BasicBlock *BB, Loop *L);
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Instruction *getDomInst(Instruction *I1, Instruction *I2);
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BasicBlock::iterator findInsertPos(Function &Fn, GlobalVariable *GV,
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BasicBlock *&PosBB);
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Instruction *genBitCastInst(Function &Fn, GlobalVariable *GV);
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bool tryReplaceTLSCandidates(Function &Fn);
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bool tryReplaceTLSCandidate(Function &Fn, GlobalVariable *GV);
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};
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} // end namespace llvm
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#endif // LLVM_TRANSFORMS_SCALAR_TLSVARIABLEHOIST_H
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